1. Field of the Invention
This invention relates to a novel chemically modified vegetable oil-based industrial fluid having superior performance properties and to methods for its preparation.
2. Description of the Prior Art
Most of the lubricants currently in daily use originate from petroleum base stocks that are toxic to environment, making it increasingly difficult for safe and easy disposal. There has been a increasing demand for xe2x80x9cgreenxe2x80x9dlubricants [Rhee, I., NLGI Spokesman, 60(5):28 (1996)] in recent years due to concerns about loss of mineral oil-based lubricants to the environment and increasingly strict government regulations controlling their use. Losses from accidental spillage and non-recoverable usage can result in ground water contamination and pose a threat to animal and plant life.
Vegetable oils such as rapeseed oil and high oleic varieties of other oils are considered to be potential candidates to replace conventional mineral oil-based lubricating oils and synthetic esters [Randles, S. J. et al.; J. Syn. Lubr., 9:145 1992); Asadauskas, S. et al.; Lub. Eng., 52:877 (1996)]. Vegetable oils are non-toxic, renewable resources and lower cost alternatives to synthetic fluids. The primary industrial application of vegetable oil use has been in the area of biodegradable hydraulic fluids. They have very low volatility due to high molecular weight of triacylglycerol molecule and narrow range of viscosity change with temperature. The ester linkages deliver inherent lubricity and enable the oils to adhere to metal surfaces. Further, vegetable oils have higher solubilizing capacity for contaminants and additives than mineral base fluids.
The most serious disadvantage of vegetable oils is their poor oxidative stability [Becker, R. et al.; Lubr. Sci., 8:95 (1996); Gapinski, R. E. et al.; SAE Tech Pap. 941785, pages 1-9 (1994)], primarily due to the presence of bis allylic protons. These protons are highly susceptible to radical attack and subsequently undergo oxidative degradation to form polar oxy compounds. This oxy-polymerization process ultimately results in insoluble deposit formation, and an increase in oil acidity and viscosity. Vegetable oils also show poor corrosion protection [Ohkawa, S. A. et al.; SAE Tech paper 951038, pages 55-63 (1995)], and the presence of ester functionality render these oils susceptible to hydrolytic breakdown [Rodes, B. N., et al.; SAE Tech paper 952073, pages 1-4 (1995)]. Therefore contamination with water in the form of emulsion must be prevented at every stage. Low temperature studies have also shown that most vegetable oils undergo cloudiness, precipitation, poor flow and solidification at cold temperatures.
We have now discovered a novel class of chemically-modified vegetable oils and chemically-modified vegetable oil-based industrial fluids as well as methods for producing them from triglyceride oils having unsaturated fatty acid substituents. The resultant vegetable oil derivatives, having diester substitution at the sites of unsaturation, have utility in hydraulic fluids, lubricants, metal working fluids and the like.
In accordance with this discovery, it is an object of this invention to provide novel vegetable oil derivatives.
It is also an object of the invention to provide environmentally-friendly vegetable oil-based industrial fluids having acceptable low temperature performance properties.
It is a specific object of this invention to provide vegetable oil-based industrial fluids having acceptable thermal and oxidative stability and low temperature fluidity.
Another object of the invention is to introduce a new use for vegetable oils and to expand the market for an agricultural commodity.
A further object of the invention is produce industrial fluids that reduce the demand on petroleum resources and that are biodegradable.
It is also an object of the invention to provide both a single-step and a two-step synthetic route for converting sites of unsaturation in triglyceride fatty esters to diester functionality.
Other objects and advantages of this invention will become readily apparent from the ensuing description. dr
FIG. 1 is a graph comparing the percent of insoluble deposit of soybean oil (⋄), epoxidized soybean oil (xe2x96xa1) and di-OHx-soybean oil (xcex94) during thin film micro-oxidation (TFMO) at 175xc2x0 C. under air flow (20 ml/minute).